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[OT] Best FM aerial?
I know it is not for a Digital TV,but...
....is there a better FM aerial than one of the 'halo' ones that at least 50% of people seem to have? I have also seen ones that look like really old (1950s) TV aerials which I presume are for FM. TIA Dave R -- |
On Sun, 9 Jan 2005 13:02:53 -0000, David W.E. Roberts
wrote: I know it is not for a Digital TV,but... ...is there a better FM aerial than one of the 'halo' ones that at least 50% of people seem to have? I have also seen ones that look like really old (1950s) TV aerials which I presume are for FM. The 'halo' is a non-aerial and you should not even consider it. Except in fringe areas, all you need for FM is a simple dipole. If this doesn't provide enough signal, a three-element yagi will give better reception. It's very unlikely that you will need anything better than this. Arthur |
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wrote in message oups.com... take a look at http://www.wrightsaerials.tv/verthalo.html Bill Ah - thanks for this. I knew I had seen a critique of the 'halo' somewhere. Now looking for a vertical half wave dipole on the net. So far they seem to be aimed at transmission, and/or PMR466 use. Any pointers to a handy supplier welcome. I presume the sheds etc. just stock the 'halo' (if anything). Cheers Dave R |
"Arthur" wrote in message ... On Sun, 9 Jan 2005 13:02:53 -0000, David W.E. Roberts wrote: I know it is not for a Digital TV,but... ...is there a better FM aerial than one of the 'halo' ones that at least 50% of people seem to have? I have also seen ones that look like really old (1950s) TV aerials which I presume are for FM. The 'halo' is a non-aerial and you should not even consider it. Except in fringe areas, all you need for FM is a simple dipole. If this doesn't provide enough signal, a three-element yagi will give better reception. It's very unlikely that you will need anything better than this. Arthur Thanks - presumably the Yagi will be directional? If so, is there a site like Woolfbane to rell me where to point it? Cheers Dave R |
David W.E. Roberts wrote:
wrote in message oups.com... take a look at http://www.wrightsaerials.tv/verthalo.html Bill Ah - thanks for this. I knew I had seen a critique of the 'halo' somewhere. Now looking for a vertical half wave dipole on the net. So far they seem to be aimed at transmission, and/or PMR466 use. Any pointers to a handy supplier welcome. Here's a dipole: http://cpc.farnell.com/jsp/endecaSea...KU=AFROD&N=401 but you can get a full kit from Maplins including (IIRC) 10m: http://www.maplin.co.uk/Module.aspx?...dID =&doy=9m1 -- Steve - www.digitalradiotech.co.uk - Digital Radio News & Info Find the cheapest Freeview, DAB & MP3 Player Prices: http://www.digitalradiotech.co.uk/fr..._receivers.htm http://www.digitalradiotech.co.uk/da...tal_radios.htm http://www.digitalradiotech.co.uk/mp...rs_1GB-5GB.htm http://www.digitalradiotech.co.uk/mp...e_capacity.htm |
On Sun, 9 Jan 2005 16:47:36 -0000, David W.E. Roberts
wrote: The 'halo' is a non-aerial and you should not even consider it. Except in fringe areas, all you need for FM is a simple dipole. If this doesn't provide enough signal, a three-element yagi will give better reception. It's very unlikely that you will need anything better than this. Arthur Thanks - presumably the Yagi will be directional? If so, is there a site like Woolfbane to rell me where to point it? Yes, a yagi will be directional but is fairly large and you will probably not need it. Signal levels are in very high in most areas, so that portable radios can work without an external aerial - this is why a crap piece of metal like a halo will often give a satisfactor signal. If you replaced it with a metal bucket it would work just as well. Where are you? Arthur |
"David W.E. Roberts" wrote in message ... snip The 'halo' is a non-aerial and you should not even consider it. Except in fringe areas, all you need for FM is a simple dipole. If this doesn't provide enough signal, a three-element yagi will give better reception. It's very unlikely that you will need anything better than this. Arthur Thanks - presumably the Yagi will be directional? If so, is there a site like Woolfbane to rell me where to point it? Found http://www.zoo.co.uk/~nw/soundscapes...ry/dipole.html which confirms it is directional. Also confirms that it is tuned to receive a certain band of frequencies. I think FM covers about 80-110 MHz so I presume one aerial will cover all this :-) Aha! http://forum.digitalspy.co.uk/board/...3&page=2&pp=25 says "Maplin sell them for 15-25 quid. alternatively, get yourself down to B&Q and get a band II FM dipole for a tenner, borrow someone's hacksaw and cut each length to around 66cm, re-assemble and voila - you have a DAB dipole!" which implies that B&Q do supply dipoles :-) I guess http://www.maplin.co.uk/Module.aspx?...ID =6&doy=9m1 or http://www.maplin.co.uk/Module.aspx?...ID =6&doy=9m1 should do me, although I guess the dipole will be fine as I am currently using the 'negative gain' halo on my partially dismounted old aerial mast. B&Q website is no help, so I guess I'll nip up to the nearest store first thing in the morning. Cheers Dave R |
Thanks - presumably the Yagi will be directional? If so, is there a site like Woolfbane to rell me where to point it? The vertical dipole is (in the main) omni directional, although if mounted mid mast, the mast can affect this. A horizontally polarized three element band II yagi is directional. I have one of these pointed at Sutton Coldfield from above Evesham. The reflector is the longest element and goes at the back. To decide which way to point it you need to decide which stations you will mainly be wanting. Most people point it at their main nationals FM transmitter (as most relays are vertically polarized.) There is little point in directing a horizontally polarized array at a vertically transmitting relay station. My array picks up the BBC stations and Birmingham locals perfectly, but other locals from Malvern and Lark Stoke are also excellent due to high local signal strength. A vertical dipole struggled on the Birmingham stations and was not good enough at my rural location. If reception on a portable receiver is okay on the rod aerial, try a vertical dipole first, unless you are trying to receive out of area broadcasts. |
"Arthur" wrote in message ... On Sun, 9 Jan 2005 16:47:36 -0000, David W.E. Roberts wrote: The 'halo' is a non-aerial and you should not even consider it. Except in fringe areas, all you need for FM is a simple dipole. If this doesn't provide enough signal, a three-element yagi will give better reception. It's very unlikely that you will need anything better than this. Arthur Thanks - presumably the Yagi will be directional? If so, is there a site like Woolfbane to rell me where to point it? Yes, a yagi will be directional but is fairly large and you will probably not need it. Signal levels are in very high in most areas, so that portable radios can work without an external aerial - this is why a crap piece of metal like a halo will often give a satisfactor signal. If you replaced it with a metal bucket it would work just as well. Where are you? Arthur Thanks - will go for the dipole first. I am in Felixstowe, Suffolk. IP11 postcode |
David W.E. Roberts said the following on 09/01/2005 17:23:
Aha! http://forum.digitalspy.co.uk/board/...3&page=2&pp=25 says "Maplin sell them for 15-25 quid. alternatively, get yourself down to B&Q and get a band II FM dipole for a tenner, borrow someone's hacksaw and cut each length to around 66cm, re-assemble and voila - you have a DAB dipole!" which implies that B&Q do supply dipoles :-) What ever Texas Homecare are called now (Homebase?) sell Dipoles too I got my dipole from Maplin, alas i can't use it in my bedroom so make do with the communal TV aerial (thats not needed since Saga joined NOW Notts). Kev |
On Sun, 9 Jan 2005 18:43:33 -0000, David W.E. Roberts
wrote: Thanks - will go for the dipole first. I am in Felixstowe, Suffolk. IP11 postcode A dipole will suit you fine. Your local BBC transmitter is Manningtree - you can almost see it from Felixstowe. - Arthur |
Hello,
Please do not even consider a HALO ! A horizontally polarised folded dipole bent into a circular shape with a MINUS figure for gain - so it will reduce signal strength compared to a dipole. If it's for normal use then get a VHF 88-108MHz dipole kit from B&Q for example. Just make sure you mount it so that the centre conductor of the coaxial cable is connected to the element sticking up in the air. A lot of people can't even get that bit right and put them upside down. If it's for indoor use, get a small junction box and two bits of wire about 70cm long, just hang it in the loft for local stations. If it's for a specific station a fair distance away, you might need to buy a beam. "David W.E. Roberts" wrote in message ... I know it is not for a Digital TV,but... ...is there a better FM aerial than one of the 'halo' ones that at least 50% of people seem to have? I have also seen ones that look like really old (1950s) TV aerials which I presume are for FM. TIA Dave R -- |
"David W.E. Roberts" wrote in message ... I know it is not for a Digital TV,but... ...is there a better FM aerial than one of the 'halo' ones that at least 50% of people seem to have? I have also seen ones that look like really old (1950s) TV aerials which I presume are for FM. Having searched the local TV shop (Hughes) and shed (Homebase) and come up empty I travelled to B&Q. The Masterplug dipole they sell is not a single aerial (one up, one down) but a loop (like the slidy part of a trombone). Each half is about 750mm long - one side (once assembled) is continuous (i.e 1.5m) and the other side feeds into the bracket where the co-ax attaches. I am hopint this is a GOOD THING and that the issue with the 'hallo' aerial is to do with it's bent shape and not the double aerial because what I seem to have is a 'halo' aerial beforeit is bent into the donut shape. Yours in hope Dave R P.S. I bought 2 (one for a neighbour) and of the two, one has a strange bit of metal instead of a nut and so can't be assembled. Realistically, it will be far cheaper to walk up to my local Homebase and find a replacement nut than to drive to B&Q and back to exchange the aerial. Still, 50% failure rate isn't that good. |
"David W.E. Roberts" wrote in message ... "David W.E. Roberts" wrote in message ... I know it is not for a Digital TV,but... ...is there a better FM aerial than one of the 'halo' ones that at least 50% of people seem to have? I have also seen ones that look like really old (1950s) TV aerials which I presume are for FM. Having searched the local TV shop (Hughes) and shed (Homebase) and come up empty I travelled to B&Q. The Masterplug dipole they sell is not a single aerial (one up, one down) but a loop (like the slidy part of a trombone). Each half is about 750mm long - one side (once assembled) is continuous (i.e 1.5m) and the other side feeds into the bracket where the co-ax attaches. I am sure that I have read somewhere that there should be a minimum distance between the dipole and the mast.. However I can't find this at the moment. The Masterplug aerial comes complete with a wall mount. I have a bracket which will clamp the horizontal pole to my mast, but the aerial will only be about 200mm away from the mast. Is this O.K. or should I be looking to extend the horizontal mounting pole? TIA Dave R |
"David W.E. Roberts" wrote:
I am sure that I have read somewhere that there should be a minimum distance between the dipole and the mast.. However I can't find this at the moment. Probably, the greater the better, but that puts a strain on the pole, and a twisting strain when the wind blows. I do wonder if the pole causes a hole in the FM reception in that direction. A halo might be worse than a dipole in most directions, but I suspect that it's more even directionally, and better at picking up signals from behind the pole. -- Dave Farrance |
"David W.E. Roberts" wrote in message ... "David W.E. Roberts" wrote in message ... I know it is not for a Digital TV,but... ...is there a better FM aerial than one of the 'halo' ones that at least 50% of people seem to have? I have also seen ones that look like really old (1950s) TV aerials which I presume are for FM. Having searched the local TV shop (Hughes) and shed (Homebase) and come up empty I travelled to B&Q. The Masterplug dipole they sell is not a single aerial (one up, one down) but a loop (like the slidy part of a trombone). Each half is about 750mm long - one side (once assembled) is continuous (i.e 1.5m) and the other side feeds into the bracket where the co-ax attaches. Yaargh! The co-ax which comes with the kit is nice looking hefty black stuff (looks like CF100). However when stripped back there is virtually bugger all copper braid. The copper coloured sheathing is silver on the inside, which suggests it is not copper foil. Fortunately I have a reel of SLx PF100 which seems to have real copper foil and decent braiding, but why sell a kit with such crap cable? [on the up side the brown cable I currently have installed, and was considering replacing, has a really hefty copper braid so may be able to stay] I have connected this up temporarily ('F' plug into aerial and push plug at other end) using the supplied cable and tried it in my radio in the kitchen. Hand held, it performs worse than the 'halo' on the roof and seems best when held horizontally. I don't know how realistic a test this is but I am wondering how well it will perform on the roof :-( Now if will only stop raining.... Dave R |
On Mon, 10 Jan 2005 14:07:03 -0000, David W.E. Roberts
wrote: I am sure that I have read somewhere that there should be a minimum distance between the dipole and the mast.. However I can't find this at the moment. The Masterplug aerial comes complete with a wall mount. I have a bracket which will clamp the horizontal pole to my mast, but the aerial will only be about 200mm away from the mast. Is this O.K. or should I be looking to extend the horizontal mounting pole? To get true omni-directional reception with a vertical dipole you would need to have it spaced at least a half-wave (i.e. the length of the dipole aerial) away from the parallel pole. However you don't need omni because you are on the coast! Space it a quarter-wave (half the dipole length) away from the pole, but make sure you put it on the *west* side of the pole. This will improve the coverage to the west and put a notch to the east, so that you get less interference from the continent during abnormal conditions. Arthur |
On Mon, 10 Jan 2005 15:19:57 -0000, "David W.E. Roberts"
wrote: "David W.E. Roberts" wrote in message ... "David W.E. Roberts" wrote in message ... I know it is not for a Digital TV,but... ...is there a better FM aerial than one of the 'halo' ones that at least 50% of people seem to have? I have also seen ones that look like really old (1950s) TV aerials which I presume are for FM. Having searched the local TV shop (Hughes) and shed (Homebase) and come up empty I travelled to B&Q. The Masterplug dipole they sell is not a single aerial (one up, one down) but a loop (like the slidy part of a trombone). Each half is about 750mm long - one side (once assembled) is continuous (i.e 1.5m) and the other side feeds into the bracket where the co-ax attaches. Yaargh! The co-ax which comes with the kit is nice looking hefty black stuff (looks like CF100). However when stripped back there is virtually bugger all copper braid. The copper coloured sheathing is silver on the inside, which suggests it is not copper foil. Fortunately I have a reel of SLx PF100 which seems to have real copper foil and decent braiding, but why sell a kit with such crap cable? [on the up side the brown cable I currently have installed, and was considering replacing, has a really hefty copper braid so may be able to stay] I have connected this up temporarily ('F' plug into aerial and push plug at other end) using the supplied cable and tried it in my radio in the kitchen. Hand held, it performs worse than the 'halo' on the roof and seems best when held horizontally. I don't know how realistic a test this is but I am wondering how well it will perform on the roof :-( Now if will only stop raining.... Dave R This test is not a realistic one at all. The reception on your roof will be a lot stronger than your kitchen. I have a dipole, and noticed a big difference between loft mounting & roof mounting. BTW, a folded dipole is fine, as long as it's not bent into a halo ;-) Marky P. |
"Arthur" wrote in message ... On Mon, 10 Jan 2005 14:07:03 -0000, David W.E. Roberts wrote: I am sure that I have read somewhere that there should be a minimum distance between the dipole and the mast.. However I can't find this at the moment. The Masterplug aerial comes complete with a wall mount. I have a bracket which will clamp the horizontal pole to my mast, but the aerial will only be about 200mm away from the mast. Is this O.K. or should I be looking to extend the horizontal mounting pole? To get true omni-directional reception with a vertical dipole you would need to have it spaced at least a half-wave (i.e. the length of the dipole aerial) away from the parallel pole. However you don't need omni because you are on the coast! Space it a quarter-wave (half the dipole length) away from the pole, but make sure you put it on the *west* side of the pole. This will improve the coverage to the west and put a notch to the east, so that you get less interference from the continent during abnormal conditions. Arthur Looks like I need to extend the pole :-( Full length (with bracket in the middle) is 1530cms. Presumably this is half wave (wavelength of 3m?). [Aarrgh again - if the radio is Frequency Modulation then what is the wavelength of the carrier which is having its frequency modulated?] This would imply putting the dipole about 750cms away from the mast. Which means I need about 500mm of extension. Another thing. With the 'trombone' shape, should the twin diploles be in line with the signal source, or at right angles? i.e. looking from the transmitter, should you see one dipole (with the other hidden behind it) or see both dipoles as you would with a TV aerial? Seems logical (working from TV aerials) that the oval should be at right angles to the signal, but perhaps logic misleads. Especially as this would require me to put the dipole on the north or south of the mast given the shape of the mounting (which is at right angles to the oval, not pointing through the middle). Think I need a sit down and a medicinal :-) Dave R |
On Mon, 10 Jan 2005 17:13:19 -0000, David W.E. Roberts
wrote: Looks like I need to extend the pole :-( Full length (with bracket in the middle) is 1530cms. Presumably this is half wave (wavelength of 3m?). Yes - 100 MHz is a wavelength of 3 metres, so a half-wave dipole is 1.5m long. And a quarter-wave spacing from the pole would be 0.75m. Don't be too fussed about the spacing - dipoles are far less critical in dimensions than multi-elements eg yagis. If you reduced it to 0.5m you will not get an ideal pattern, but you can afford to lose a bit of signal and will not notice it except on distant stations. [Aarrgh again - if the radio is Frequency Modulation then what is the wavelength of the carrier which is having its frequency modulated?] This would imply putting the dipole about 750cms away from the mast. Which means I need about 500mm of extension. 100 MHz is the carrier frequency. The frequeny deviation is negligible compared to the carrier frequency so all of the signal is within the bandwidth of the dipole. With the 'trombone' shape, should the twin diploles be in line with the signal source, or at right angles? i.e. looking from the transmitter, should you see one dipole (with the other hidden behind it) or see both dipoles as you would with a TV aerial? Absolutely not important. Fit it whichever way is easiest. If there is no balun then check that the element connected to the coax inner is at the top. Also run and fix the coax along the horizontal support boom to the mast - don't cut the corner. -Arthur |
"David W.E. Roberts" wrote in message ... I know it is not for a Digital TV,but... ...is there a better FM aerial than one of the 'halo' ones that at least 50% of people seem to have? I have also seen ones that look like really old (1950s) TV aerials which I presume are for FM. Progress report: new dipole is installed - standing off from mast by about 1.5m. The signal is slightly better than the 'halo' in its current orientation (i.e. 45 degrees). Four solid bars on the NAD receiver instead of 3-4 from the old aerial. Thanks to all for help/advice. Pictures will be posted for constructive comment once the scaffolding is down. Cheers Dave R |
"David W.E. Roberts" wrote in message ... snip Progress report: new dipole is installed - standing off from mast by about 1.5m. The signal is slightly better than the 'halo' in its current orientation (i.e. 45 degrees). Four solid bars on the NAD receiver instead of 3-4 from the old aerial. Having one of those "Don't know why I bother" moments. Having neglected to label up the co-ax terminals for the FM aerial feeds in the loft I decided to do the usual trick of unplugging them one by one from the amplifier in the loft and waiting for the signal to disappear at the radio. This proved more difficult than I thought as the signal didn't seem to go away when the co-ax was unplugged from the amp. In the bedroom I was getting 3 bars on the co-ax alone and 4 bars when the aerial was connected through the amp. I also got 4 bars when I used a femalefemale connector to bypass the amp and connect the bedroom system directly to the roof aerial. In the lounge, I swapped the leads around (old TV lead goes direct outside to aerial, co-ax to loft does FM). I get no signal from the fly lead, but if I plug into the old TV aerial then I get a reasonable FM signal. So: do I just have very dodgy co-ax which acts as an acceptable FM aerial? If not, what is going on? Next step is a wire coathanger in the back of the tuner - and see it this out-performs the roof installed aerial. Hardly seems worth all the hassle of installing an aerial for a minor signal boost. Next thing to do is see if I can get a clean feed using all PF100 to the NAD in the bedroom to see if that improves the signal at all. Ho hum. Dave R |
On Wed, 12 Jan 2005 17:56:59 +0000, David W.E. Roberts wrote:
"David W.E. Roberts" wrote in message ... snip Progress report: new dipole is installed - standing off from mast by about 1.5m. The signal is slightly better than the 'halo' in its current orientation (i.e. 45 degrees). Four solid bars on the NAD receiver instead of 3-4 from the old aerial. Having one of those "Don't know why I bother" moments. snip In the bedroom I was getting 3 bars on the co-ax alone and 4 bars when the aerial was connected through the amp. I also got 4 bars when I used a femalefemale connector to bypass the amp and connect the bedroom system directly to the roof aerial. snip Next thing to do is see if I can get a clean feed using all PF100 to the NAD in the bedroom to see if that improves the signal at all. Ho hum indeed. Latest results a Co-ax in the wall (no amp or aerial) 2 bars Aerial direct to tuner (new co-ax) 3 bars Aerial through amp.(old + new co-ax) 4 bars All three setups gave what sounded like acceptable stereo reception. Now puzzled as to why my previous test gave a better result using [new co-ax plus the old co-ax in the wall] than new co-ax all the way. Both setups used the same aerial feed, the same femalefemale coupler. Perhaps the signal strength has gone down as night falls. Whatever, signal must be getting into the old co-ax so something isn't right. Dave R |
On Wed, 12 Jan 2005 14:54:04 -0000, David W.E. Roberts
wrote: "David W.E. Roberts" wrote in message ... I know it is not for a Digital TV,but... ...is there a better FM aerial than one of the 'halo' ones that at least 50% of people seem to have? I have also seen ones that look like really old (1950s) TV aerials which I presume are for FM. Progress report: new dipole is installed - standing off from mast by about 1.5m. The signal is slightly better than the 'halo' in its current orientation (i.e. 45 degrees). Four solid bars on the NAD receiver instead of 3-4 from the old aerial. Thanks to all for help/advice. Pictures will be posted for constructive comment once the scaffolding is down. Cheers Dave R Might be better to post them *before* the scaffolding is down. Arthur |
On Wed, 12 Jan 2005 14:54:04 -0000, "David W.E. Roberts"
wrote: "David W.E. Roberts" wrote in message ... I know it is not for a Digital TV,but... ...is there a better FM aerial than one of the 'halo' ones that at least 50% new dipole is installed - standing off from mast by about 1.5m. I didn't bother extending the arm on my FM dipole, and connected it as it was (about 8 inches from mast roughly). Works exceptionally well, though I have noticed some attenuation from the east (where the mast masks the aerial). Whether extending the distance from aerial to mast would've eliminated the masking I don't know, but it's not important. Marky P. |
On Wed, 12 Jan 2005 18:23:32 +0000, David WE Roberts
wrote: On Wed, 12 Jan 2005 17:56:59 +0000, David W.E. Roberts wrote: "David W.E. Roberts" wrote in message ... snip Progress report: new dipole is installed - standing off from mast by about 1.5m. The signal is slightly better than the 'halo' in its current orientation (i.e. 45 degrees). Four solid bars on the NAD receiver instead of 3-4 from the old aerial. Having one of those "Don't know why I bother" moments. snip In the bedroom I was getting 3 bars on the co-ax alone and 4 bars when the aerial was connected through the amp. I also got 4 bars when I used a femalefemale connector to bypass the amp and connect the bedroom system directly to the roof aerial. snip Next thing to do is see if I can get a clean feed using all PF100 to the NAD in the bedroom to see if that improves the signal at all. Ho hum indeed. Latest results a Co-ax in the wall (no amp or aerial) 2 bars Aerial direct to tuner (new co-ax) 3 bars Aerial through amp.(old + new co-ax) 4 bars All three setups gave what sounded like acceptable stereo reception. Now puzzled as to why my previous test gave a better result using [new co-ax plus the old co-ax in the wall] than new co-ax all the way. Both setups used the same aerial feed, the same femalefemale coupler. Perhaps the signal strength has gone down as night falls. Whatever, signal must be getting into the old co-ax so something isn't right. Dave R Now you've really confused me! OK, let's try to get this straight. Co-ax in the wall (no amp or aerial) 2 bars. Right, that must be the FM signal just dropping itself into the end of the cable (or right through the cable it's cheap or knackered). Aerial direct to tuner (new co-ax) 3 bars. OK, this would be the most accurate reading. If your cable is CT100 or equivalent & around 10-12m in length, there will be very little loss at FM frequencies. Aerial through amp (old & new co-ax) 4 bars. Now, I believe the new co-ax is from aerial to amp, then old co-ax from amp to tuner. In this case, the amp is improving the signal through the old co-ax, hence there will be less loss. Beware of tuner signal strength meters though. The stronger the amp, the more bars will light up on the tuner. This isn't necessarily an indication of a better signal from the aerial, just the amp adding it's own boosted signal, therefore giving an inaccurate reading. In my naive day, I bought a 40dB amp to put in line with my FM aerial to improve the signal. The meter was whacked right up to full on all receivable stations! But when the excitement died down & I actually listened to the radio, the quality of reception was just the same. Hissy stations were still hissy regardless of what the meter said, all because the amp was producing a false reading. Sorry for going on a bit. Hope I didn't lose you in the translation somewhere. Marky P. |
Four solid bars on the NAD receiver instead of 3-4 from the old
aerial. That's probably 10dB! Bill |
"Arthur" wrote in message ... On Wed, 12 Jan 2005 14:54:04 -0000, David W.E. Roberts wrote: snip Pictures will be posted for constructive comment once the scaffolding is down. Cheers Dave R Might be better to post them *before* the scaffolding is down. Arthur Will do. For the moment, think of those postcards of 'Wales at Night'. Tomorrow morning I will expose you to the full horror. Cheers Dave R |
"Marky P" wrote in message ... On Wed, 12 Jan 2005 18:23:32 +0000, David WE Roberts wrote: snip Now you've really confused me! snip For a confused person you seem remarkably lucid ;-)) Thing that is bugging/puzzling me is the amount of signal I get off the co-ax. It may not be a good, clean signal but the FM receivers seem to work fine on it. As Bill posts, the one bar on the tuner may be a major gain in signal strength and quality, however.... I guess if the co-ax can pick up FM radio then it is noisy. I think I have found a use for the rest of my new cable :-) Cheers Dave R |
Thing that is bugging/puzzling me is the amount of signal I get off
the co-ax. This sounds as if the receiver is not matched to the feeder. Could it be that the receiver has a balanced RF input, even though the socket is coaxial? If that is the case it would pick up a lot of signal on the coax, and would make all attempts to use an aerial at the other end of the cable rather pointless. If the receiver does have a balanced input (be it 75ohm or 300ohm), you need a balun. If the aerial socket on the receiver is isolated from the chassis you can test my hypothesis by connecting the braid and leaving the inner unconnected. If this results in a signal of any strength being received then the socket is connected to a balanced tuner input. Bill Bill |
"Arthur" wrote in message ... On Wed, 12 Jan 2005 14:54:04 -0000, David W.E. Roberts wrote: snip Might be better to post them *before* the scaffolding is down. Arthur Again apologies for image size. http://www.chelsworth-lodge.nildram....NewAerials.jpg The chimney brackets are a bit close together and grip less of the pole than is ideal, but they are pretty hefty and feel very solid and secure. The pole grip compromise comes from two things. (1) There isn't that much chimney above the ridge to get wires around. (2) The aim is to get the TV aerial as high as possible to see over Felixstowe docks. The standoff for the FM aerial is also a compromise because the aerial comes with a wall/chimney mount so I had to source additional bits and pieces. However it is the suggested 1.5m away from the main pole, and pointing towards Manningtree. I have not charged the scaffolding firm for the free advert :-) Cheers Dave R |
On Thu, 13 Jan 2005 10:47:47 -0000, David W.E. Roberts
wrote: "Arthur" wrote in message ... On Wed, 12 Jan 2005 14:54:04 -0000, David W.E. Roberts wrote: snip Might be better to post them *before* the scaffolding is down. Arthur Again apologies for image size. http://www.chelsworth-lodge.nildram....NewAerials.jpg The chimney brackets are a bit close together and grip less of the pole than is ideal, but they are pretty hefty and feel very solid and secure. The pole grip compromise comes from two things. (1) There isn't that much chimney above the ridge to get wires around. (2) The aim is to get the TV aerial as high as possible to see over Felixstowe docks. The standoff for the FM aerial is also a compromise because the aerial comes with a wall/chimney mount so I had to source additional bits and pieces. However it is the suggested 1.5m away from the main pole, and pointing towards Manningtree. I have not charged the scaffolding firm for the free advert :-) Thanks for the picture. I'm sure that as the acknowledged expert on aerial installation, Bill will give the definitive judgement, but my comments are these: - The standoff for the FM dipole is greater than necessary. As previously discussed, a quarter-wave spacing is probably all you need. The long boom, hit with a sideways wind, may cause some twisting of the brackets - or worse, of the whole pole which will take the TV aerial off its correct heading. - the overall height in comparison with the bracket spacing, looks just a *little* long for an exposed coastal position. But at least you are not on a hilltop. - I note you have used nylon cable ties to fix the coax to the pole, and trust that you have not fallen into the trap of over-tightening them which causes crushing of the coax. Arthur |
On Thu, 13 Jan 2005 11:50:54 -0000, Arthur wrote:
Thanks for the picture. I'm sure that as the acknowledged expert on aerial installation, Bill will give the definitive judgement, but my comments are these: - The standoff for the FM dipole is greater than necessary. As previously discussed, a quarter-wave spacing is probably all you need. The long boom, hit with a sideways wind, may cause some twisting of the brackets - or worse, of the whole pole which will take the TV aerial off its correct heading. - the overall height in comparison with the bracket spacing, looks just a *little* long for an exposed coastal position. But at least you are not on a hilltop. - I note you have used nylon cable ties to fix the coax to the pole, and trust that you have not fallen into the trap of over-tightening them which causes crushing of the coax. Also I'm not sure why you have put a 'dog leg' on the dipole support. Couldn't you have fitted the dipole dirctly onto to stand-off from the main pole? Arthur |
Thanks for the picture. I'm sure that as the acknowledged expert on
aerial installation, Cringe making! Bill will give the definitive judgement, but my comments are these: The standoff for the FM dipole is greater than necessary. As previously discussed, a quarter-wave spacing is probably all you need. The long boom, hit with a sideways wind, may cause some twisting of the brackets - or worse, of the whole pole which will take the TV aerial off its correct heading. Agreed. The FM aerial is made by Vision (but rebadged I expect). They have a stupid short side arm, but there's really no need to put it this far from the mast. Decide on a direction you don't care about (Europe?) and put the aerial on the side of the mast away from that direction, about a quarter wavelength away. By the way, those aerials have better bandwidth than a simple dipole. They are significantly better at the ends of the FM band. the overall height in comparison with the bracket spacing, looks just a *little* long for an exposed coastal position. But at least you are not on a hilltop. Agreed. Is the mast a scaffolding tube? I hope so. If so it should be OK. I note you have used nylon cable ties to fix the coax to the pole, and trust that you have not fallen into the trap of over-tightening them which causes crushing of the coax. Agreed. Also, the masthead amp will be out of reach if it ever goes wrong. They should always be fitted within reach. Having said all this the job is a damn sight better than most DIY aerials I get to see! Bill |
On 13 Jan 2005 04:04:17 -0800, "
wrote: Thanks for the picture. I'm sure that as the acknowledged expert on aerial installation, Cringe making! Bill will give the definitive judgement, but my comments are these: The standoff for the FM dipole is greater than necessary. As previously discussed, a quarter-wave spacing is probably all you need. The long boom, hit with a sideways wind, may cause some twisting of the brackets - or worse, of the whole pole which will take the TV aerial off its correct heading. Agreed. The FM aerial is made by Vision (but rebadged I expect). They have a stupid short side arm, but there's really no need to put it this far from the mast. Decide on a direction you don't care about (Europe?) and put the aerial on the side of the mast away from that direction, about a quarter wavelength away. By the way, those aerials have better bandwidth than a simple dipole. They are significantly better at the ends of the FM band. the overall height in comparison with the bracket spacing, looks just a *little* long for an exposed coastal position. But at least you are not on a hilltop. Agreed. Is the mast a scaffolding tube? I hope so. If so it should be OK. I note you have used nylon cable ties to fix the coax to the pole, and trust that you have not fallen into the trap of over-tightening them which causes crushing of the coax. Agreed. Also, the masthead amp will be out of reach if it ever goes wrong. They should always be fitted within reach. Having said all this the job is a damn sight better than most DIY aerials I get to see! Bill My one's nice :-) I'll post a pic when I get hold of a decent camera. Marky P. |
"Arthur" wrote in message ... On Thu, 13 Jan 2005 11:50:54 -0000, Arthur wrote: snip Also I'm not sure why you have put a 'dog leg' on the dipole support. Couldn't you have fitted the dipole dirctly onto to stand-off from the main pole? Arthur As I think Bill indicated, things are not that simple. The dipole is integral with a short arm (the 'dog leg') which comes as standard with a wall bracket. So as using a standard pole and clamp involves right angle joins, this forces me to have a dog leg. If I understand 'wavelength' correctly then a full wave is about 3m, 1/2 wave is about 750cms, 1/4 wave is about 375cms. The arm built onto the dipole gives a maximum spacing from the mast of 200cms which is nearer 1/8 wave. I was previously advised (by someone) that half wave was a good distance to be from the mast. That is roughly the current spacing (1.5m). I admit it looks ungainly and like a very large lever. I will look at adjusting it. However they may come and take the scaffolding down tomorrow :-) Cheers Dave R |
"Arthur" wrote in message ... On Thu, 13 Jan 2005 10:47:47 -0000, David W.E. Roberts wrote: snip - The standoff for the FM dipole is greater than necessary. As previously discussed, a quarter-wave spacing is probably all you need. The long boom, hit with a sideways wind, may cause some twisting of the brackets - or worse, of the whole pole which will take the TV aerial off its correct heading. ** See other response ** - the overall height in comparison with the bracket spacing, looks just a *little* long for an exposed coastal position. But at least you are not on a hilltop. ** However they are bigger than the average bracket :-) A bit of judicious swinging on the pole didn't seem to shift them in the slightest. Biggest downside of the setup is mast flex . At least it survived the recent blow better than the old mast :-( ** - I note you have used nylon cable ties to fix the coax to the pole, and trust that you have not fallen into the trap of over-tightening them which causes crushing of the coax. Arthur I experimented and the tie leaves a little notch under the locking point which just accomodates the cable nicely. On my rooftop survey I noted that other aerials seemed to have tape around them (I meant to ask the NG about this but forgot) but I just happened to have this large bag of cable ties, so..... I also wondered how long tape lasts in the sun and wind, and if a special tape is used. The cynic in me guessed that a reel of tape is cheaper than a bag of cable ties. Cheers Dave R |
On Thu, 13 Jan 2005 21:53:16 -0000, David W.E. Roberts
wrote: "Arthur" wrote in message ... On Thu, 13 Jan 2005 10:47:47 -0000, David W.E. Roberts wrote: snip - The standoff for the FM dipole is greater than necessary. As previously discussed, a quarter-wave spacing is probably all you need. The long boom, hit with a sideways wind, may cause some twisting of the brackets - or worse, of the whole pole which will take the TV aerial off its correct heading. ** See other response ** - the overall height in comparison with the bracket spacing, looks just a *little* long for an exposed coastal position. But at least you are not on a hilltop. ** However they are bigger than the average bracket :-) A bit of judicious swinging on the pole didn't seem to shift them in the slightest. Biggest downside of the setup is mast flex . At least it survived the recent blow better than the old mast :-( ** - I note you have used nylon cable ties to fix the coax to the pole, and trust that you have not fallen into the trap of over-tightening them which causes crushing of the coax. Arthur I experimented and the tie leaves a little notch under the locking point which just accomodates the cable nicely. On my rooftop survey I noted that other aerials seemed to have tape around them (I meant to ask the NG about this but forgot) but I just happened to have this large bag of cable ties, so..... I also wondered how long tape lasts in the sun and wind, and if a special tape is used. The cynic in me guessed that a reel of tape is cheaper than a bag of cable ties. I personally have only used cable ties once on airspaced coax, and after that experience went back to duct tape which seems to last forever if applied carefully. I note in Bill's recently posted picture about Emley that he uses tape on his professional installations. No doubt he will tell you what sort it is. Arthur |
I note in Bill's recently posted picture about Emley
that he uses tape on his professional installations. No doubt he will tell you what sort it is. Tikkitape. Only black is UV proof. I used to use RS Components tape but the quality was variable. Cable ties aren't good really, but yes you can accomodate the cable under the cusp of the ratchet thingy. Tape is better though. Bill |
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